U.S. Geological Survey
Fact Sheet 2007-3047
Version 1.0

Hawaiian Duck’s Future Threatened by Feral Mallards

By Kimberly J. Uyehara, Andrew Engilis, Jr., and Michelle Reynolds

2007

The greatest threat to the future of the Koloa maoli as a unique species is cross-breeding with the introduced Mallard duck (A. platyrhynchos). This photograph shows feral Mallards, including “barnyard ducks,” at Wailoa River State Park on Hawai‘i. (Photograph by K. Uyehara.)

Nearly 70 percent of Hawai‘i’s native bird species are found nowhere else on Earth, and many of these species are declining or in danger of extinction. Although the Hawaiian Islands were once home to a remarkable diversity of waterfowl, only three species remain—the Hawaiian Goose (Nēnē), Laysan Duck, and Hawaiian Duck (Koloa maoli)—all Federally endangered. The Koloa maoli is the only Hawaiian bird threatened by “genetic extinction” from hybridization with an invasive species—feral Mallard ducks. U.S. Geological Survey (USGS) biologists in Hawai‘i are working to find the causes of bird endangerment and ways to prevent extinction of the Koloa maoli and other threatened birds.